Adjustable absorber designs for implantable device

ABSTRACT

A system for manipulating energy transferred by members defining a joint. The system includes a first attachment structure configured to be attached to a first member of the joint and a second attachment structure configured to be attached to a second member of the joint. There is also an adjustable energy absorbing device attached to the first attachment structure and second attachment structure, wherein adjusting the energy absorbing device changes the load manipulating characteristics of the energy absorbing device.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.11/743,097, filed May 1, 2007, a continuation-in-part of U.S.application Ser. No. 11/743,605, filed May 2, 2007, acontinuation-in-part of U.S. application Ser. No. 11/775,139, filed Jul.9, 2007, a continuation-in-part of U.S. application Ser. No. 11/775,149,filed Jul. 9, 2007 and a continuation-in-part of U.S. application Ser.No. 11/775,145, filed Jul. 9, 2007, the entire disclosures of which areexpressly incorporated herein by reference.

BACKGROUND

Joint replacement is one of the most common and successful operations inmodern orthopaedic surgery. It consists of replacing painful, arthritic,worn or diseased parts of a joint with artificial surfaces shaped insuch a way as to allow joint movement. Osteoarthritis is a commondiagnosis leading to joint replacement. Such procedures are a lastresort treatment as they are highly invasive and require substantialperiods of recovery. Total joint replacement, also known as total jointarthroplasty, is a procedure in which all articular surfaces at a jointare replaced. This contrasts with hemiarthroplasty (half arthroplasty)in which only one bone's articular surface at a joint is replaced andunincompartmental arthroplasty in which the articular surfaces of onlyone of multiple compartments at a joint (such as the surfaces of thethigh and shin bones on just the inner side or just the outer side atthe knee) are replaced. Arthroplasty as a general term, is anorthopaedic procedure which surgically alters the natural joint in someway. This includes procedures in which the arthritic or dysfunctionaljoint surface is replaced with something else, procedures which areundertaken to reshape or realigning the joint by osteotomy or some otherprocedure. As with joint replacement, these other arthroplastyprocedures are also characterized by relatively long recovery times andtheir highly invasive procedures. A previously popular form ofarthroplasty was interpositional arthroplasty in which the joint wassurgically altered by insertion of some other tissue like skin, muscleor tendon within the articular space to keep inflammatory surfacesapart. Another previously done arthroplasty was excisional arthroplastyin which articular surfaces were removed leaving scar tissue to fill inthe gap. Among other types of arthroplasty are resection(al)arthroplasty, resurfacing arthroplasty, mold arthroplasty, cuparthroplasty, silicone replacement arthroplasty, and osteotomy to affectjoint alignment or restore or modify joint congruity. When it issuccessful, arthroplasty results in new joint surfaces which serve thesame function in the joint as did the surfaces that were removed. Anychondrocytes (cells that control the creation and maintenance ofarticular joint surfaces), however, are either removed as part of thearthroplasty, or left to contend with the resulting joint anatomy.Because of this, none of these currently available therapies arechondro-protective.

A widely-applied type of osteotomy is one in which bones are surgicallycut to improve alignment. A misalignment due to injury or disease in ajoint relative to the direction of load can result in an imbalance offorces and pain in the affected joint. The goal of osteotomy is tosurgically re-align the bones at a joint and thereby relieve pain byequalizing forces across the joint. This can also increase the lifespanof the joint. When addressing osteoarthritis in the knee joint, thisprocedure involves surgical re-alignment of the joint by cutting andreattaching part of one of the bones at the knee to change the jointalignment, and this procedure is often used in younger, more active orheavier patients. Most often, high tibial osteotomy (HTO) (the surgicalre-alignment of the upper end of the shin bone (tibia) to address kneemalalignment) is the osteotomy procedure done to address osteoarthritisand it often results in a decrease in pain and improved function.However, HTO does not address ligamentous instability—only mechanicalalignment. HTO is associated with good early results, but resultsdeteriorate over time.

Other approaches to treating osteoarthritis involve an analysis of loadswhich exist at a joint. Both cartilage and bone are living tissues thatrespond and adapt to the loads they experience. Within a nominal rangeof loading, bone and cartilage remain healthy and viable. If the loadfalls below the nominal range for extended periods of time, bone andcartilage can become softer and weaker (atrophy). If the load risesabove the nominal level for extended periods of time, bone can becomestiffer and stronger (hypertrophy). Finally, if the load rises too high,then abrupt failure of bone, cartilage and other tissues can result.Accordingly, it has been concluded that the treatment of osteoarthritisand other bone and cartilage conditions is severely hampered when asurgeon is not able to precisely control and prescribe the levels ofjoint load. Furthermore, bone healing research has shown that somemechanical stimulation can enhance the healing response and it is likelythat the optimum regime for a cartilage/bone graft or construct willinvolve different levels of load over time, e.g. during a particulartreatment schedule. Thus, there is a need for devices which facilitatethe control of load on a joint undergoing treatment or therapy, tothereby enable use of the joint within a healthy loading zone.

Certain other approaches to treating osteoarthritis contemplate externaldevices such as braces or fixators which attempt to control the motionof the bones at a joint or apply cross-loads at a joint to shift loadfrom one side of the joint to the other. A number of these approacheshave had some success in alleviating pain but have ultimately beenunsuccessful due to lack of patient compliance or the inability of thedevices to facilitate and support the natural motion and function of thediseased joint. The loads acting at any given joint and the motions ofthe bones at that joint are unique to the body that the joint is a partof. For this reason, any proposed treatment based on those loads andmotions must account for this variability to be universally successful.The mechanical approaches to treating osteoarthritis have not taken thisinto account and have consequently had limited success.

Prior approaches to treating osteoarthritis have also failed to accountfor all of the basic functions of the various structures of a joint incombination with its unique movement. In addition to addressing theloads and motions at a joint, an ultimately successful approach mustalso acknowledge the dampening and energy absorption functions of theanatomy, and be implantable via a minimally invasive technique. Priordevices designed to reduce the load transferred by the natural jointtypically incorporate relatively rigid constructs that areincompressible. Mechanical energy (E) is the action of a force (F)through a distance (s) (i.e., E=F^(x)s). Device constructs which arerelatively rigid do not allow substantial energy storage as the forcesacting on them do not produce substantial deformations—do not actthrough substantial distances—within them. For these relatively rigidconstructs, energy is transferred rather than stored or absorbedrelative to a joint. By contrast, the natural joint is a constructcomprised of elements of different compliance characteristics such asbone, cartilage, synovial fluid, muscles, tendons, ligaments, etc. asdescribed above. These dynamic elements include relatively compliantones (ligaments, tendons, fluid, cartilage) which allow for substantialenergy absorption and storage, and relatively stiffer ones (bone) thatallow for efficient energy transfer. The cartilage in a joint compressesunder applied force and the resultant force displacement productrepresents the energy absorbed by cartilage. The fluid content ofcartilage also acts to stiffen its response to load applied quickly anddampen its response to loads applied slowly. In this way, cartilage actsto absorb and store, as well as to dissipate energy.

With the foregoing applications in mind, it has been found to benecessary to develop effective structures for mounting to body anatomy.Such structures should conform to body anatomy and cooperate with bodyanatomy to achieve desired load reduction, energy absorption, energystorage, and energy transfer. These structures should include mountingmeans for attachment of complementary structures across articulatingjoints.

For these implant structures to function optimally, they must not causean adverse disturbance to joint motion. Therefore, what is needed is anapproach which addresses both joint movement and varying loads as wellas complements underlying or adjacent anatomy.

SUMMARY OF THE DISCLOSURE

Briefly and in general terms, the present disclosure is directed towardstreating diseased or mal-aligned body joints, typically affected byosteoarthritis, using an adjustable energy absorbing device withoutlimiting the range of motion of the patient's articulating joint. Thedevices of the present invention accomplish one or more of: absorbingenergy during normal gait, reducing load on at least a portion of thenatural joint, load transferring or bypassing, energy cushioning, andload sharing or redistribution. In addition, both energy dampening andshock absorption are considered in effecting such load manipulations.Further, the particular anatomy of a patient is considered in thecontemplated approaches in that loads on desired portions of anatomy aremanipulated without overloading healthy surfaces. In a preferredembodiment, the present invention adds an energy absorber to the jointto reduce energy transferred through the natural joint. One embodimentincludes a system for manipulating or absorbing energy transferred bymembers defining a joint. The system includes a first attachmentstructure configured to be attached to a first member of the joint and asecond attachment structure configured to be attached to a second memberof the joint. There is also an adjustable energy absorbing or absorptiondevice attached to the first attachment structure and second attachmentstructure, wherein adjusting the energy absorbing or absorption devicealters the load manipulating or absorbing function of the device. Thissystem may be used to treat a knee joint, or other joint, affected withosteoarthritis and variable amounts of energy absorbing or absorptionoccurs while the members follow the path of motion of the joint.

The device can be intraoperatively or post-operatively adjusted. Forexample, the device can be adjusted post-operatively as further or lessload manipulation becomes necessary. Moreover, the device can beactivated and adjusted to absorb energy to desired degree or can bedeactivated so that no energy absorbing occurs such as just subsequentto implantation. In this way, a natural healing process where tissue andbone at the interventional site grows over the implanted structure helpsin fixation of the structure prior to activating its load manipulatingcapabilities. Various approaches are contemplated to accomplishadjustment through a patient's skin. In this regard, components of thedevice are translated to achieve desired load manipulating as well as toprohibit accidental adjustments of the device. Moreover, feedbacksystems are incorporated into the device to both indicate translationduring adjustment as well as locking and unlocking adjustablecomponents. Such feedback can come in the form of sound orproprioperception.

In one embodiment, the implantable system may include a dual springenergy absorbing device. Still in another embodiment, the system mayinclude a single spring energy absorbing device. In either embodiment,adjusting the compression of the springs/spring alters the character ofthe load the energy absorption system manipulates in response toarticulation of members to which it is attached. The load manipulatingprofile the system provides may be adjusted during surgery when theenergy absorption system is implanted onto a joint, or after a patienthas recovered from surgery. Adjustment of the load manipulatingcharacteristics may be performed multiple times as needs andcircumstances surrounding the patient change over time. Alternatively,the amount of load the system can manipulate may be adjusted byreplacing the springs/spring of the device with springs/spring having adifferent measure of stiffness.

In other approaches, adjustment is provided by selectively positioningmounts to which absorbers are attached. Moreover, in certainembodiments, adjustment can be provided by adjusting link ends incombination with or to the exclusion of adjusting springs forming theload bearing structure. Adjusting a point of translatable components ofa link such that the link does not carry loads beyond a predeterminedamount and the natural joint carries the load above that amount is alsocontemplated so as to control forces being transferred to the bases ofan energy absorbing device. Such bases can be made of flexible materialfor absorbing forces. Additionally, desired adjustment can be achievedthrough mechanical aspects of a machined spring itself.

In one embodiment of the energy absorbing system, the adjustable energyabsorbing device includes an arbor shaft and an adjustable assembly or acollar slidably attached to the arbor shaft. The arbor shaft may beconnected to an arbor having an arbor base. The assembly or collar isconfigured to translate along a portion of the length of the arbor shaftand lock into a position on the shaft. In certain embodiments, thecollar may be a split collar, spring loaded collar, a twist and pulllocking collar, stop collar, “Grip Fast” collar, or any other collarthat can be configured to lock and unlock along a shaft. The assembly orcollar may also be any collar configured to translate over threads ofthe arbor shaft. The adjustable energy absorbing device may also includea piston shaft that slides within a lumen of the arbor shaft. The lumencan pass completely through the arbor base to provide structure suitedto avoid the piston from locking up with the arbor shaft. The pistonshaft includes a piston that is connected to a base of the piston arbor.

In one embodiment, the adjustable energy absorbing device includes acompression spring disposed over the arbor shaft between the collar andthe piston base. Adjusting the position of the collar over the arborshaft changes the compression of the compression spring, therebychanging a load manipulating profile of the energy absorbing system. Ina dual spring embodiment the adjustable energy absorbing device includesa first spring and a second spring disposed over a first arbor shaft anda second arbor shaft, respectively.

In another embodiment, the energy absorbing device may include a springstop or assembly that is free floating along an arbor shaft between astationary arbor base and a compression spring. The compression springis disposed over the arbor shaft between the spring stop or assembly anda piston base. The piston base includes a piston that slides within alumen of the arbor shaft. To adjust the load manipulatingcharacteristics of the system in this embodiment, the device includes aplurality of shims attached to the arbor base on a pivot disposedadjacent to the spring stop. The shims are configured to be individuallyrotated and slid in between the arbor base and the spring stop orassembly to move the spring stop or assembly along the arbor shafttowards the piston base, thereby increasing the compression of thespring when a load is applied to the spring. Shims may also be rotatedand slid out from between the arbor base and the spring stop orassembly, thereby decreasing the compression of the spring when a loadis applied to the spring.

Yet another embodiment of an energy absorbing device includes an arborhaving a first shaft and a second shaft, the first and second shaftseach having a lumen extending at least partially through each of thefirst and second shafts. A collar is slidably engaged to the first andsecond shafts, and the collar is configured to lock into a positionalong the lengths of the first and second shafts. There is also a pistonbase having a first piston and a second piston extending from the pistonbase, with the first and second pistons configured to slide within thelumens of the first and second arbor shafts, respectively. Again, theanchor base can be equipped with through holes in communication with thelumen which received the piston shafts. A first spring is disposed overthe first arbor shaft between the collar and the piston base arbor, anda second spring is disposed over the second arbor shaft between thecollar and the piston base. Adjusting the position of the collar overthe first and second arbor shafts changes the compression of the firstand second springs, which alters the load manipulating characteristicsof the energy absorbing device.

In one embodiment, the collar of the energy absorbing device may includean adjustment core and an adjustment block being arranged to slidinglyengage together. Sliding the adjustment core and adjustment blocktowards each other unlocks the collar from the first and second arborshafts. The adjustment core and adjustment block each include an armextending towards the piston base. In one embodiment, the piston basemay include a first piston wall and a second piston wall that extendtowards the arbor base, and are configured to slide along the arms ofthe adjustment core and adjustment block, respectively. Still in anotherembodiment, the arms of the adjustment core and adjustment block eachinclude a tooth, and the first and second piston walls of the pistonarbor include a slot that engage the teeth of the arms to connect thepiston walls with the collar.

One embodiment of a method for treating a joint includes attaching afirst attachment structure to a first member of the joint and attachinga second attachment structure to a second member of the joint. An energyabsorbing device is then attached to the first attachment structure andsecond attachment structure, and the character of load manipulating ofthe energy absorbing device is adjusted to meet the needs of thepatient. In treating a knee joint, the device can be implantedextra-capsular and/or to variably change knee kinematics.

In one embodiment, adjusting the load manipulating characteristics ofthe energy absorbing device as a function of the movement of membersdefining a joint involves translating a collar or assembly over an arborshaft of the energy absorbing device to change the compression of aspring disposed over the shaft when a load is applied to the spring. Themethod of adjusting the energy absorbing device may also includeremoving any load from the spring before translating the collar over theshaft. Load may be removed from the spring by flexing the joint with thesystem attached to the members of the joint. A load will generally beapplied to the spring when the joint is extended. In certainembodiments, adjusting the energy absorbing device may include insertinga tool into the collar or assembly to unlock the collar or assembly,thereby allowing the collar or assembly to translate over the shaft. Inother embodiments, the collar or assembly can be unlocked by squeezingor pushing arms or wings associated with the collar or assembly toovercome a spring biasing force that locks the collar or assembly ontothe shaft. Once the desired load capability of the device is set byadjusting the absorber or the spring, the collar or assembly is thenlocked into position along the length of the shaft.

Adjustments may be done through or over the skin of a patient. In someembodiments, an audible sound such as a click is created by the collaror adjustment assembly when it is unlocked or locked to provide feedbackto the physician. Also, audible sounds or tactile feedback can beprovided to the physician as the collar or adjustment assembly istranslated along the length of the shaft. Such feedback can beincorporated both into unlocking the energy absorbing device as well asfor translating components of the device to new positions. Structure canbe further incorporated into the implanted system to prevent accidentalunlocking and/or translation as well as to facilitate translationthrough the skin. In the latter regard, the motion or placement ofmembers defining the target joint and secondary structures such as asecondary compression spring can be utilized.

Other features of the energy absorbing system and device will becomeapparent from the following detailed description, taken in conjunctionwith the accompanying drawings, which illustrate, by way of example, theprinciples of the embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view, depicting an embodiment of an energyabsorbing system mounted at a knee joint at full extension;

FIG. 1B is a perspective view, depicting the embodiment shown in FIG. 1Awith the knee joint flexed to 90°;

FIG. 2A is a partial cross-sectional view, depicting one embodiment ofan adjustment sub-structure;

FIG. 2B is a partial cross-sectional view, depicting another embodimentof an adjustment sub-structure;

FIG. 2C is an enlarged view, depicting an adjustment ring of FIG. 2Bshown in a ratchet engaged state;

FIG. 2D is an enlarged view, depicting the adjustment ring of FIG. 2C ina ratchet release state;

FIGS. 3A and 3B are partial views, depicting one embodiment of an energyabsorbing device;

FIG. 4A is a partial perspective view, depicting one embodiment of anenergy absorbing device with a split collar;

FIG. 4B is a cross-sectional view of the split collar shown in FIG. 4Ain a locked configuration;

FIG. 4C is a cross-sectional view of the split collar shown in FIG. 4Ain an unlocked configuration;

FIG. 5A is a partial perspective view, depicting one embodiment of anenergy absorbing device with a split collar having compressible wings;

FIG. 5B is a cross-sectional view of the split collar shown in FIG. 5Ain a locked configuration;

FIG. 5C is a cross-sectional view of the split collar shown in FIG. 5Ain an unlocked configuration;

FIG. 5D is a perspective view, depicting one embodiment of an energyabsorbing device with a split collar having one compressible wing;

FIG. 6A is a perspective view, depicting one embodiment of an energyabsorbing device with a locking collar;

FIG. 6B is a partial perspective view of the locking collar shown inFIG. 6A in a locked configuration;

FIG. 6C is a cross-sectional view taken along line 6C-6C of FIG. 6B ofthe locking collar;

FIG. 7A is a partial perspective view, depicting another embodiment ofan energy absorbing device with a locking collar;

FIG. 7B is a partial perspective view of the locking collar shown inFIG. 7A;

FIG. 7C is a cross-sectional view taken along line 7C-7C of FIG. 7B ofthe locking collar;

FIG. 8A is a planar view, depicting another embodiment of an energyabsorbing device with a locking collar;

FIG. 8B is a partial perspective view of the locking collar shown inFIG. 8A;

FIG. 8C is a partial perspective view showing the ball bearings of thelocking collar shown in FIG. 8A;

FIG. 8D is a cross-sectional view of the locking collar shown in FIG.8B;

FIGS. 9A through 9D depict various views of another embodiment of alocking collar;

FIG. 10A is a perspective view, depicting another embodiment of anenergy absorbing device with a locking collar in a locked configuration;

FIG. 10B is a perspective view, depicting the energy absorbing device ofFIG. 10A in an unlocked configuration;

FIG. 10C is a partial perspective view showing the locking collar ofFIG. 10A;

FIG. 10D is a cross-sectional view of the locking collar shown in FIG.10A;

FIGS. 11A through 11C show various views of another embodiment of alocking collar;

FIGS. 12A through 12H show one embodiment of an energy absorbing deviceand a method for adjusting the load of the device;

FIG. 13 is a perspective view, depicting another embodiment of an energyabsorbing device;

FIG. 14 is a perspective view, depicting yet another embodiment of anenergy absorbing device;

FIG. 15 is a perspective view, depicting another embodiment of an energyabsorbing device;

FIG. 16 is a perspective view, depicting a sheath placed over an energyabsorbing device;

FIG. 17A is a perspective view, depicting an embodiment of a singlespring energy absorbing device;

FIG. 17B is a partial perspective view of the energy absorbing deviceshown in FIG. 17A;

FIG. 18A is a perspective view, depicting another embodiment of a singlespring energy absorbing device;

FIG. 18B is a partial perspective view of the energy absorbing deviceshown in FIG. 18A;

FIG. 19A is a perspective view, depicting an embodiment of a singlespring energy absorbing device;

FIG. 19B is a partial perspective view of the energy absorbing deviceshown in FIG. 19A;

FIGS. 20A and 20B depict partial perspective views showing anotherembodiment of a single spring energy absorbing device;

FIGS. 21A and 21B depict partial perspective views showing anon-circular single spring energy absorbing device with thickened walls;

FIG. 22A is a perspective view, depicting an embodiment of a circularlink element;

FIG. 22B is a partial perspective view, depicting the circular linkelement of FIG. 22A;

FIG. 23A is a perspective view, depicting another embodiment of acircular link element;

FIG. 23B is a partial perspective view, depicting the circular linkelement of FIG. 23A;

FIG. 24A is a perspective view, depicting an embodiment of a springstop;

FIG. 24B is a partial perspective view, depicting the spring stop ofFIG. 24A disposed on a shaft;

FIGS. 25A and 25B depict partial perspective views of another embodimentof a spring stop disposed on a shaft;

FIG. 26 is a partial perspective view, depicting yet another embodimentof a spring stop disposed on a shaft;

FIG. 27 is a partial perspective view, depicting another embodiment of aspring stop disposed on a shaft; and

FIG. 28 is a perspective view, depicting an embodiment of a circularlink with zero load on a spring showing flexible helical shims beingdisposed around a shaft to adjust the load of the circular link.

FIG. 29A is a perspective view, depicting a further embodiment of anenergy absorbing device;

FIG. 29B is a perspective view, depicting an opposite side of the deviceof FIG. 29A with compression springs removed;

FIG. 29C is a perspective view, depicting the adjustment core plates ofFIGS. 29A and 29B;

FIG. 30A is a perspective view, depicting yet a further embodiment of anenergy absorbing device;

FIG. 30B is a perspective view, depicting an opposite side of the deviceof FIG. 30A with compression springs removed;

FIG. 30C is a perspective view, depicting the adjustment core assemblyof FIGS. 30A and 30B;

FIG. 31A is a perspective view, depicting yet a further embodiment of anenergy absorbing device;

FIG. 31B is a partial perspective view, depicting an opposite side ofthe device of FIG. 31A with compression springs removed;

FIG. 31C is a perspective view, depicting the core adjustmentsubassembly of FIGS. 31A and 31B;

FIG. 32A is a perspective view, depicting an energy absorbing deviceincluding center and side squeeze mechanisms;

FIG. 32B is a perspective view, depicting an opposite side of the devicedepicted in FIG. 32A;

FIG. 32C is a perspective view, depicting the device of FIG. 32B withcompression springs removed;

FIG. 32D is a perspective exploded view, depicting components of theadjustable subassembly of FIGS. 32A-C;

FIG. 33A is a perspective view, depicting an energy absorbing deviceincluding an adjustable spacer;

FIG. 33B is a perspective view, depicting the device of FIG. 33A withthe spacer removed;

FIG. 33C is a perspective view, depicting the device of FIGS. 33A and33B with a nut of the adjustable spacer subassembly removed;

FIG. 34A is a perspective view, depicting an energy absorbing deviceincluding adjustable spacer structure;

FIG. 34B is a perspective view, depicting the device of FIG. 34A withcompression springs removed;

FIG. 35A is a perspective view, depicting an energy absorbing deviceincluding adjustable structure interacting with piston shafts;

FIG. 35B is a perspective view, depicting the device of FIG. 35A withcompression springs removed;

FIG. 35C is a perspective view, depicting the device of FIG. 35B withadjustment core and block structure removed;

FIG. 35D is a perspective view, depicting an alternate approach to anadjustment assembly;

FIG. 35E is an exploded view, depicting the components of FIG. 35D;

FIG. 36A is a perspective view, depicting an interlocking link withthreaded adjustment structure;

FIG. 36B is a perspective view, depicting the device of FIG. 36A with aslider removed;

FIG. 37 is a perspective view, depicting an approach to a link which canbe intra-operatively or post-operatively activated.

DETAILED DESCRIPTION

Referring now to the drawings, which are provided by way of example andnot limitation, the disclosed embodiments are directed towards apparatusand methods for treating the knee joint. However, these embodiments mayalso be used in treating other body joints, and to alleviate painassociated with the function of diseased or misaligned members forming abody joint without limiting the range of motion of the joint. Theembodiments described below relate to apparatuses and methods foradjusting the amount of load an energy absorbing device can manipulate.Some embodiments include an energy absorbing device including a dualspring member and other embodiments include the use of a single springmember.

Certain of the embodiments include energy absorbing devices designed tominimize and complement the dampening effect and energy absorptionprovided by the anatomy of the body, such as that found at a body joint.It has been postulated that to minimize pain, load manipulation orabsorption of 1-40% of forces, in varying degrees, may be necessary.Variable load manipulation or energy absorption in the range of 5-20%can be a target for certain applications.

In body anatomy incorporating energy absorbing systems as describedbelow, less forces are transferred to the bones and cartilage of themembers defining the joint, and a degree of the forces between bodymembers is absorbed by the energy absorbing system. In one embodiment,the energy absorbing system can be initially configured to eliminate,variably reduce or manipulate loads to a desired degree, and to be lateradjusted or altered as patient needs are better determined or change.

In applications to the knee joint, the energy absorbing system can bedesigned to absorb medial compartment loads in a manner that completelypreserves the articulating joint and capsular structures. One embodimentof the present invention is load bypassing knee support system comprisedof a kinematic load absorber, two contoured base components and a set ofbone screws. The implanted system is both extra articular and extracapsular and resides in the subcutaneous tissue on the medial (orlateral) aspect of the knee. The device is inserted through two smallincisions above the medial femoral and tibial condyles. The basecomponents are fixed to the medial cortices of the femur and tibia usingbone screws. The energy absorber having a spring value of about twentypounds can provide therapeutic benefit for patients of 275 pounds orless. Higher spring forces would provide greater reduction in joint loadand may correlate to greater symptom (i.e., pain) relief.

It has been recognized that knee forces have multiple components. Thereare a quadriceps force F_(Q) and a ground reaction force F_(G) directedgenerally longitudinally along a leg and there are lateral compartmentforces F_(L) and medial compartment forces F_(M). There is, however, noconventional clinical measure of F_(M) or F_(L). On the other hand,there are non-axial knee forces which result in a moment being appliedacross the joint referred to as a knee adduction moment. The kneeadduction moment (KAM) can be measured clinically. The measurements areuseful as KAM can be considered to be a clinical surrogate measure forknee forces.

It has been further observed that a high knee adduction momentcorrelates with pain. That is, it would be expected that a group ofpeople with diseased joints having lower KAM may not have pain whereasindividuals with a relatively higher KAM would experience pain. Thus, anactive reduction of knee adduction moment can reduce pain. The system ofthe present invention reduces the KAM of the patient.

It has also been found that a medial compartment of a knee of an averageperson with osteoarthritis can benefit from an absorber set forcompression between 1 mm and 10 mm, and preferably 3-6 mm with a springor absorber element that accommodates a range from 20-60 pounds. In apreferred embodiment, the absorber is set for about 4 mm of suchcompression and a pre-determined load of about 40 pounds.

In each of the disclosed embodiments, various features can beincorporated from other of the disclosed embodiments. Thus, audible andtextile feedback sub-systems can be incorporated in the disclosedembodiments to both indicate translation of load adjustment structure aswell as to exhibit locking and unlocking of subcomponents. Moreover,each of the contemplated embodiments can include springs machined toprovide desirable energy absorbing which varies as the spring iscompressed during various degrees of flexion and extension of jointmarkers to which the energy absorbing device is attached. The term“spring” is used throughout the description but it is contemplated toinclude other energy absorbing and compliant structures can be used toaccomplish the functions of the invention as described in more detailbelow. Additionally, any of the various disclosed approaches toachieving adjustment through a patient's skin, either through directengagement with the energy absorbing device with a tool or by applyingforces to the device through the surface of the skin can be incorporatedto fill a perceived need.

In certain situations, it has been found to be a benefit to implant theenergy absorbing device in an inactivated condition, only later takingsteps, perhaps several weeks later, to place the device into anactivated state. In this way, the device can become further affixed tobone as the bone and surrounding tissue grows over portions of thedevice. Accordingly, each of the disclosed embodiments can be soimplanted and later activated and adjusted through a patient's skin.

Further, various approaches to adjusting the energy absorbing device arecontemplated and disclosed below. That is, various approaches toadjusting structure between piston and arbor structure as well asadjusting mounts to which the piston and arbor structures are configuredto engage are disclosed. In the former regard, adjustable collars andadjustable link ends are contemplated approaches.

Referring now to FIGS. 1A-1C, one embodiment of an energy absorbingsystem 100 is shown with proximal 102 and distal 104 base componentspositioned upon first 106 and second 108 members, respectively of atypical body joint. Here, the terminal end portions of the femur andtibia are depicted without surrounding tissue. It is noted that portionsof the base components are contoured to match potential mountingsurfaces of the femur and tibia. Also shown is an energy absorbingdevice 110 that is configured between and mounted to the basecomponents. FIG. 1A shows the knee joint at full extension with loadbeing applied to springs 112 of the energy absorbing device, whereasFIG. 1B shows the knee joint flexed to 90° with zero load being appliedto the springs by virtue of the springs 112 being shorter than thelength of the piston shafts 126. The energy absorbing device lengthensas the knee swings from full extension to flexion and subsequentlyshortens as the knee swings from flexion to full extension such that thesprings begin to be compressed between the ends of the device to absorbthe load that the knee articulating surfaces normally would experience.The energy absorbing device and base components are mounted across thejoint such that once the springs have achieved a predetermined amount ofcompression, and therefore load, the articulating surfaces of the kneethen begin to carry the load in combination with the energy absorbingdevice such that the energy absorbing device does not “bottom out”. Thevarious energy absorbing devices in the present application are shownwithout a protective covering or sheath but it is contemplated that theycan be within a protective covering or sheath to protect the movingelements from impingement by surrounding tissues and to prevent thedevices from damaging surrounding tissue.

Still referring to FIGS. 1A-1C, one embodiment of an energy absorbingdevice 110 includes a piston base 114 and an arbor base 116. The pistonbase is connected to a first or proximal mount 118 that is in connectionwith the proximal or first base component 102. On the other end of theenergy absorbing device, the arbor base is connected to a second ordistal mount 120 that is in connection with the distal or second basecomponent 104. As shown in FIG. 1C, holes 121 are formed in the arborbase 116 to allow and/or contract fluid flow through the arbor duringmotion. A valve can be added to convert the structure into a pneumaticabsorber. A first or proximal end 122 of the springs 112 is inconnection with or in contact with the piston base, and a second ordistal end of the springs are in contact with a spacer 124 when the kneejoint is extended as shown in FIG. 1A. The size of the spacer 124 can beadjusted to affect the amount of compression of the springs. Also, thespacer 124 can be formed of material providing compliance or springbehavior for added energy absorbing or as a built-in overload safetymechanism.

During flexion and extension of the knee joint, piston shafts 126 (notshown) of the piston base slide within arbor shafts (See FIG. 1B) of thearbor base. Although two compression springs are shown in the energyabsorbing device, one or more springs may be used. The configuration ofthe springs may be varied to minimize device size while maximizing itsenergy absorbing capabilities. Moreover, various types of springs suchas coaxial or leaf springs can be employed and the spring structure canbe placed serially and adjusted one by one.

The energy absorbing system has the capacity to absorb energy inaddition to transfer energy from the joint. The energy absorption of thedual or single spring can be expressed as the product of force anddisplacement. Although actual springs are used to show variousembodiments, these elements could also be substituted with a material orother device with spring-like characteristics (e.g., an elastomericmember). Such elastomers include thermoplastic polyurethanes such asTecoflex, Tecothane, Tecoplast, Carbothene, Chronthane and ChronoFlex(grades AR, C, AL) which also could be employed as a dampener. Moreover,materials such as Pebax, C-flex, Pellathane and silicone and siliconefoam can also be employed.

In other embodiments, the energy absorbing device may include dampeningdevices such as dash pots. In these embodiments, the spring element is astorage or absorber device while the dashpot acts to dissipate theenergy. Such embodiments or other structure defining a shock absorberwhich alter the velocity of displacement of the spring can be employedto thereby alter the energy absorption behavior. Although moretraditional dampening devices may be used with the energy absorbingdevice, these elements could also be substituted with a material orother device with dampening characteristics (e.g., a small pore sponge).

For one embodiment of system 100, a pre-operative session is performedto assess the need at a joint and to map the articulation of the members106 and 108 forming the joint. Attachment sites are also assessedpre-operatively. During surgical intervention, a first center ofrotation location is identified along the first member of a joint. Next,access is gained to an area proximate the first center of rotationlocation and the first base component 102 is fixed upon the first memberin a manner maintaining use of the first center of rotation location. Asecond rotation location is then identified along the second member of ajoint and surgical access is obtained proximate the second rotationlocation. Subsequently, the second base component 104 is fixed along thesecond member while maintaining use of the second rotation location. Asubcutaneous channel is created between the first center of rotation andsecond rotation locations and the energy absorbing device 110 isinserted within the channel. The energy absorber is thereafter mountedto the bases. A tissue barrier, such as a sheath, may be placed aboutthe energy absorber to protect joint anatomy or exclude the device fromsurrounding tissue. The connection of the absorber 110 to the bases 102and 104 through attachable/detachable mounts 118 and 120 provides amethod for good attachment of the base to the bone and a more simplesurgical technique for installing the absorber. It also allows a sheathand/or the wear components of the absorber/mount assembly to beremoveable and/or replaceable without removing or replacing the basecomponents. It further allows the wear components of the absorber/mountassembly and the base components to be different materials. For example,the base components can be titanium or titanium alloy which promoteosteo-integration and the wear components can be much harder materialssuch as cobalt chrome (e.g., Biodur CCM Plus), ceramic, or other durablematerials that produce a minimal amount of particulate material or, ifparticulate material is generated, the smallest size of particulatematerial.

In a contemplated method, the energy absorbing device 110 can beinitially configured to eliminate or reduce loads to a desired degree,and to be later adjusted or altered as patient needs are betterdetermined or change. Accordingly, post-operative alterations arecontemplated as are adjustments resulting from changing the diameter ofa dampening component or a spring rate of a device. In this regard, itis also contemplated there be no initial or load manipulation until theinterventional site heals and the device is firmly implanted or duringan initial treatment episode to substantially reduce the effects andpain associated with a patient afflicted with osteoarthritis for a longtime. The device can provide distraction forces and carry all of theload to an extent that the joint surfaces do not experience load whenthe joint is fully load bearing. This distraction can continue for up tothree months (or preferably two months) and then later the device can beadjusted to accomplish energy absorption without distraction. Moreover,as needs change, the method can involve removal or replacement of one ormore components of the energy absorbing assembly. Further, variousdegrees of non-invasive approaches can be employed as is practical for agiven interventional procedure. Additional details and other embodimentsof an energy absorbing system and method of implantation are shown anddescribed in U.S. application Ser. No. 11/775,149, which has alreadybeen incorporated by reference.

Turning now to FIGS. 2A-D, there is shown approaches to adjusting theenergy absorbing device 110. In the approaches depicted, the deviceincludes an arbor shaft 130 including outwardly projecting and angledteeth. The shaft may form part of the arbor base 116. A spring-biasedcollar assembly 132 is further provided and configured in a lockablearrangement with the shaft. In a first approach (FIG. 2A), the collarassembly 132 is further provided with spring biased buttons 134 (hereshown biased in a closed position by an elastomeric ring) having adistant terminal end. As the buttons are each depressed inwardly, thisengagement with the teeth of the shaft disengages, thereby allowing theassembly 132 to move up or down. As the assembly 132 is so translated anaudible sound is made between the detents of the buttons and the shaft130. An observable tactile response can also be produced to alert theoperator that motion has occurred. Such feedback is contemplated to beincorporated into each of the disclosed embodiments.

In a second approach (See FIGS. 2 B-D), the spring-biased collarassembly 132 is equipped with a two piece collar spring 136 which canassume both ratchet engaged (FIG. 2C) and ratchet released (FIG. 2D)configurations. Thus, by pressing on the spring arms 138 of thisembodiment of the spring-biased collar assembly, the collar disengagesfrom the shaft 130 and is permitted to be translated longitudinally. Asa safety measure, it is to be appreciated that the angle and length ofthe teeth formed on the shaft and corresponding engaging structures ofthe collar assemblies can be configured to only allow translation if twopoints of the collar are sufficiently pressed.

In these embodiments, moving the spring biased collar assembly 132proximally towards the first base component 102 changes the storedpotential energy in the spring 112. If it is determined during or anytime after surgery that the energy absorbing system should be adjusted,the collar/piston assembly is moved distally towards the first basecomponent 102 to further compress the spring between the collar assemblyand the piston base 114.

Another embodiment of adjusting the energy absorbing device 110 is shownin FIGS. 3A and 3B. In this embodiment, the device includes twooppositely threaded spring stops 140 configured in a lockablearrangement with arbor shafts 142 of an arbor base 143, the arbor shaftshaving threads or teeth. To adjust springs 144 of the device, a rod 146with teeth can be inserted in one of two directions between the twospring stops to create rotation of the spring stops. Rotation in onedirection translates the spring stops proximally towards the arbor base,thereby decreasing the stored potential energy in the spring 142.Rotation of the stops in the opposite direction compresses the springbetween the stops and the piston base (not shown) when a load is appliedto the spring. It has also been contemplated that the rod could bethreaded and either permanently located in between the stops and rotatedvia a hex tool, or other tool, or inserted only during time ofadjustment.

Another embodiment for adjusting the energy absorbing device 110 isshown in FIGS. 4A through 4C. This embodiment includes a split collar150 having a top portion 152 and a bottom portion 154, with teeth 156 onthe bottom portion (see FIG. 4C). A pin 158 is attached to the bottomportion of the collar and is biased upward with a spring 160, whichforces the top and bottom portions to be in a closed position as shownin FIG. 4B. In the closed or locked position, the collar is locked ontothe shafts 162 of the arbor assembly 164, which include indentations orteeth 166 to engage the teeth 156 of the bottom portion of the collar.In this embodiment, a grommet 168 is press fit into the pin, providingadjustment access via a tool, such as a 1 mm needle. As shown in FIG. 4Aa sheath 170 may be disposed over the energy absorbing device, in whichcase the grommet is attached to the sheath so that the device can beadjusted without penetrating the sheath boundary. Other embodiments donot include a sheath.

To position the split collar 150 into an open configuration, a userinserts a tool into the grommet 168 and presses downward overcoming thebiasing force of the spring 160 and moving the bottom portion 154 awayfrom the top portion 152 as shown in FIG. 4C. Once the split collar lockis in the open or unlocked configuration, the springs 112 (not shown inFIGS. 4A-4C) may be adjusted by moving the split collar lock proximallyor distally along the shafts of the arbor to increase or decrease thecompression of the springs 112. Once the desired compression of thespring is achieved when the joint is at full extension, the user canremove the tool from the grommet to allow the force of spring 160 tomove the split collar into the closed or locked position.

Other embodiments are shown in FIG. 5A through 5D, and are similar tothe embodiment in FIGS. 4A through 4C. Therefore, like referencenumerals will be used to indicate like elements. In the embodiment shownin FIGS. 5A through 5C, the bottom portion 154 includes two wings 172protruding from the sides of the split collar 150. The embodiment shownin FIG. 5D includes one wing 172 protruding form only one side of thedevice. A user can unlock the device with his fingers by pushingdownward on the wings or wing to overcome the biasing force of thespring 160 and translate the collar from the closed or lockedconfiguration, shown in FIG. 5B, into the open or unlocked configurationas shown in FIG. 5C. This allows for adjustments to be made from outsideof the skin of the patient while the device is implanted. The grommet168 may or may not be included in these embodiments to allow access witha tool to unlock the split collar lock.

In one embodiment for adjusting the energy absorbing device 110 that isattached to a knee joint, the knee starts out in an extended position.The knee is then flexed to remove any load from the springs 112. Afterremoving the load from springs, the adjustment is made to the energyabsorbing device as described above in relation to each differentembodiment. Typically, the adjustment can be made over or through theskin of the patient. In one approach, the teeth on the collar locks cansupport up to about sixty-five pounds of pressure before yielding.

Another embodiment of a locking collar 180 is shown in FIGS. 6A through6C. In this embodiment, the locking collar includes a center lockingplate 182 with a top portion 184 and a bottom portion 186 connectedtogether with an integrated spring 188. The locking plate is nominallylocked in grooves 190 around the shafts 192 of the arbor 194. FIG. 6C isa cross-sectional view taken along line 6C-6C of FIG. 6B, and shows thedevice in the closed or locked configuration around the shafts. Tounlock the top and bottom portions of the center plate, a button/springmechanism 196 that separates the portions of the plate is pressed by auser. Tapered surfaces 198 of the button/spring mechanism engage taperedsurfaces 200 of the top and bottom portion of the center locking plateto push the top and bottom portions apart from one another and overcomethe biasing force of the integrated spring. This configurationdisengages the teeth of the locking plate from the grooves in theshafts. Once unlocked, the collar can be moved proximally or distally toadjust the positioning of the springs 112. The adjustment of the devicecan be done by a user squeezing both sides of the button/springmechanism at the same time through the skin of the patient, and thenreleasing the button/spring mechanism when the desired position of thespring is reached to lock the locking plate into the grooves of theshafts.

An embodiment similar to the embodiment shown in FIGS. 6A through 6C isshown in FIGS. 7A through 7C, and again, like reference numerals will beused to indicate like elements. In this embodiment, the button/springmechanism 196 has been replaced with two separate buttons 202 heldwithin the locking collar 180 by pins 204. FIG. 7C is a cross-sectionview taken along line 7C-7C of FIG. 7B. Operation of the locking collarin this embodiment is similar to the above embodiment in FIGS. 6Athrough 6C. To unlock the collar, the two buttons 202 on each side ofthe device are pressed inward to separate the top and bottom portions184 and 186 of the center locking plate 182. Once the desiredcompression of the springs 112 is achieved, the buttons are released,thereby locking the center locking plate into the grooves 190 of theshafts 192.

Another embodiment of a locking collar 210 is shown in FIGS. 8A through8D. The locking collar of this embodiment is a “Grip Fast” collar, whichincludes a set of ball bearings 212 and a tapered locking plate 214 thatlocks the mechanism in place when the internal spring 216 is loaded. Thelocking collar is transitioned into the unlocked configuration when auser presses protruding wings 218 that remove pressure from the ballbearings, which in the locked configuration are pressed against thearbor shafts. FIG. 8D is a cross-sectional view of the “Grip Fast”collar.

FIGS. 9A through 9D show another embodiment of a locking collar 220 thatincludes a first locking arm 222 and a second locking arm 224 thatengage with the teeth or grooves on the shafts of the arbor. The twolocking arms are rotated on a pin 226 and two torsion springs 228 biasthe arms in the locked position. To transition the locking collar intothe unlocked configuration, a tool is used to push down on the tips 230and 232 of the first and second locking arms, respectively, whichdisengages the locking arms from the grooves or teeth of the shafts andunlocks the collar. Once unlocked the collar can be moved to adjust thesprings of the energy absorbing system.

Another embodiment of a locking collar 240 is shown in FIGS. 10A through10D. The collar includes a set of collets 242 with small teeth 243 whichare locked into grooves 245 in shafts 244 when the spring stop 246 isforced against the set of collets. The collets and the spring stop arenominally biased against each other by two small inverted disc springs248 in the locked configuration shown in FIG. 10A. To unlock the collar,a tool 249, such as a 2×1 mm tool, is used to disengage the collar fromthe shafts by inserting the tool and rotating it, thereby separating thecollets and spring stop. This unlocked configuration is shown in FIGS.10B through 10D. To return the collar to the locked configuration, thetool is rotated in an opposite direction and removed to re-engage theteeth 245 of the collets 244 with the grooves 245 of the shafts 244.

Yet another embodiment of a stop collar 250 is shown in FIGS. 11Athrough 11C. The stop collar includes a first spring stop slider 252 anda second spring stop slider 254, each having two cutouts 256 that engageteeth or grooves 258 in shafts 260. The cutouts 256 of the first andsecond spring stops disengage the grooves on the shafts when slidperpendicular to the shafts. The first and second sliders are separatedby a single spring 262 and biased nominally in the locked position. Themechanism is disengaged once the first and second sliders are squeezedtogether to disengage the cutouts of the spring stop sliders from theshafts. FIG. 11B shows the second spring stop slider in phantom so thecutouts of the first spring stop can be seen. Also, FIG. 11C shows thecross-section taken at line 11C-11C of FIG. 11B, with the mechanism inthe locked configuration and the first spring stop engaging the groovesof the shafts.

FIGS. 12A through 12H show another embodiment of an energy absorbingdevice with a stop collar 270, and a method of adjusting the device.FIG. 12A shows the stop collar having an adjustment core 272 and anadjustment block 274 that are slidingly engaged together. The adjustmentcore and adjustment block each include a grip arm 276 that can bemanipulated or squeezed by a user. There is also a spring finger 278disposed on the adjustment block, and a tooth 280 disposed on theadjustable core near the spring finger, so that when the adjustment coreand adjustment block are squeezed together or released, the springfinger is deflected by the tooth 280 and creates an audible soundletting the user know when the stop collar is unlocked and locked. Eachgrip arm 276 includes a tooth 282 that comes in contact and rests withina slot 284 disposed on a wall 286 of the piston base 114. The pistonbase also includes pistons 288 that slide within shafts 290 of the arborbase 116. To adjust the energy absorbing device by increasing ordecreasing the compression of spring 112, the patient's leg is flexed toabout a 90° angle, and the energy absorbing device 110 will be in asimilar configuration to that shown in FIG. 12A. In this position thereis no load on the springs 112 and the stop collar 270 is locked intoposition on the teeth or grooves 292 of the shaft.

Next, as shown in FIG. 12B, the stop collar 270 is forced into theunlocked configuration by squeezing the grip arms 276 of the adjustmentcore 272 and the adjustment block 274 towards one another. An audiblesound will result when the spring finger 278 deflects off of the tooth280. The leg is then extended and the stop collar stops on the arborbase 116 at a zero load position as shown in FIG. 12C.

FIG. 12D shows the teeth 282 of the grip arms 276 hitting the pistonwalls 286. As the leg is extended, the grip arms open slightly for theteeth 282 to ride over the piston walls as shown in FIG. 12E. Finally,at complete extension, the teeth 282 fall into slots 284 of the pistonwalls, linking the piston walls with the arms of the stop collar, asshown in FIG. 12F.

With the stop collar 270 still in the unlocked configuration, the leg isnow flexed to a desired angle, and the shafts 290 extend away from thestop collar as shown in FIG. 12G. Once the desired angle and the desiredcompression of the springs 112 are reached, the arms 276 of the stopcollar are released and the leg is extended to engage the stop collarand lock into the new position in the grooves 292 of the shafts 290 asshown in FIG. 12H. When the stop collar is released, another audiblesound will be created by the spring finger 278. In one embodiment thereis also another spring finger located on the adjustment core that comesinto contact with teeth on the arbor shaft to provide an audible soundwhen the stop collar is being translated over the arbor shaft. Theseaudible sounds provide feedback to the user who may be adjusting theload of the device over the skin of the patient.

An embodiment of the energy absorbing device 110 shown in FIG. 13 issimilar to the device depicted in FIGS. 12A through 12H. In thisembodiment however, there are no piston walls, but there is a post 294on the piston base 116, and the post includes a tapered end 296 and anotch 298 near the tapered end. There is also a snap clip 300 extendingaway from the stop collar 270 with a hook 302 at its end. Instead ofteeth 282 on the grip arms 276 engaging slots 284 on the piston wall asshown in FIG. 12F of the above embodiment, in this embodiment, the hookof the snap clip engages the notch of the piston post to connect thepiston base with the stop collar.

FIG. 14 depicts another embodiment that is similar to last twoembodiments, except in this embodiment, the piston base 114 includes atapered post 310 that slides over a recess 312 in a spring tube 314. Thespring tube covers the springs 112 of the energy absorbing device 110and is in contact with the stop collar 270.

FIG. 15 shows another similar embodiment, of the collar stop 270. Inthis embodiment, the long grip arms have been replaced with short arms320 with recesses 322 configured for receiving the ends of pliers oranother tool that can be used to grip and squeeze the short arms tounlock the stop collar 270. As shown in FIG. 15, this embodiment mayalso include a sheath eyelet 323 for attachment to a sheath that coversthe energy absorbing device.

Any of the dual spring embodiments discussed above can be covered by asheath 330 as shown in FIG. 16. A sheath eyelet 332 may be attached tothe collar stop of the energy absorbing device 110. There may also be ahole 334 to gain access to a grommet associated with the stop collar tolock or unlock the device in order to adjust the device.

Referring now to FIGS. 17A and 17B, another embodiment of an energyabsorbing device 350 is shown to include a single spring 352 to absorbenergy. The device includes an arbor base 354 with an arbor casing 356and a shaft 358. Also included is a piston base 360 with a piston casing361 and a piston 362 that slides within the shaft of the arbor base. Thepiston casing is configured to slide under the arbor casing. Surroundingthe arbor shaft is a spring stop 364 with a proximal or first end 366and a distal or second end 368. There are also a plurality of shims 370that are disposed on a post 372 connected to the arbor base. The post isdisposed adjacent to the spring stop. A shim stop 374 is positioned atthe end of the post to keep the shims on the post and still allowing theshims to rotate about the post. In this embodiment there are sevenshims, that are each about 1 mm in width, however, any number of shimscan be used and they may be any width. As shown in FIG. 17A, there are aplurality of top holes 376 in the arbor casing and a plurality of bottomholes 378 in the arbor casing.

To adjust the load manipulation profile of the energy absorbing device350, a tool, such as a needle or other instrument, is inserted into themost proximal top hole 376 to activate the most proximal shim 370. Anend of the instrument inserted through the top holes will push against afirst edge 380 of the shim and rotate the shim on the post 372 so thatthe shim slides inbetween the proximal end 366 of the spring stop 364and the base of the arbor base 354. This pushes the spring stop distallyand thereby compresses the spring 352 that is abutted against the distalend 368 of the spring stop. FIG. 17B shows two shims activated. Anynumber of the shims can be activated by inserting an instrument intoconsecutive top holes starting from the proximal end. To deactivate anynumber of the shims, the instrument is inserted into the bottom holes378 disposed on the arbor casing. The end of the instrument insertedthrough the bottom holes will come into contact with a second edge 382of the shim and rotate the shim in an opposite direction to remove theshim from between the spring stop and the arbor base. Any number ofshims can be deactivated starting at the distal most activated shim.Activating and deactivating shims allow a user to adjust the compressionof the position of the spring stop and the spring. Such adjustments canbe made when the device 350 is unloaded such as during flexion.

Another embodiment of an energy absorbing device 350 a is shown in FIGS.18A and 18B, and is similar to the embodiment of the device 350 shown inFIGS. 17A and 17B, and thus, like reference numerals will be used forlike elements. In this embodiment, the arbor casing 356 includes a setof activation holes 384 on one side and a set of deactivation holes (notshown) on the opposite side of the arbor casing. This embodiment alsoincludes a spring stop 386 with a proximal end 388 and a distal end 390and a recess 392 designed to allow a plurality of shims to be stored ina deactivated state as best shown in FIG. 18B. To activate one of theshims, an instrument is inserted into the most proximal activation holewhere it engages a first edge 394 of the shim, and forces the shim torotate about the post 372 and slide in between the proximal end of thespring stop and the arbor base 354. Any number of the shims can beactivated by inserting the instrument into consecutive activation holesstarting from the proximal most hole. To deactivate the shims in thisembodiment, the instrument is inserted into the distal most deactivationholes where it engages a second edge 396 of the shim and rotates theshim back into the deactivated position. FIG. 18B shows one shimactivated.

Another embodiment of an energy absorbing device 350 b is shown in FIGS.19A and 19B. In this embodiment, there is a first set of shims 398 on afirst post 400 connected to the arbor base 354 on one side of the springstop 364, and a second set of shims 402 on a second post (not shown)connected to the arbor base on the other side of the spring stop. Thereis a first set of activation holes 404 on one side of the arbor casing356 and a second set of activation holes (not shown) on the other sideof the arbor casing. The first and second sets of shims are activated bypressing an instrument into the most proximal holes of the first andsecond sets of activation holes, which rotates the shims in between theproximal end 366 of the spring stop and the arbor base. This actioncompresses the spring 352. To deactivate the shims, an instrument isinserted through the open top slot 406 of the arbor casing 356 and thepiston casing 361 to rotate the shims back into the deactivated positionnear the wall of the spring stop. The user can deactivate any number ofactivated shims starting with the distal most activated shim.

Referring now to FIGS. 20A and 20B, an energy absorbing device 410 isshown with the spring and piston base removed for clarity. The device ofthis embodiment includes a spring stop 412 with teeth 414 threaded ontoa shaft 416 with threads 418 that is connected to the arbor base 420. Anarbor casing or wall 421 includes a first opening 422 on one side and asecond opening (not shown) on the opposite side of the casing. The firstand second openings allows a tool 424 with teeth 426, such as a needleor rod, to be inserted into the casing to mesh with the teeth of thespring stop and rotate the spring stop in one of two directions. Pushingthe tool to rotate the spring stop in one direction rotates the springstop in a distal direction down along the threads of the arbor shaft.Rotating the spring stop in the opposite direction with the tooltranslates the spring stop in a proximal direction up along the threadsof the arbor shaft. Translating the spring stop distally increases thecompression on the spring and translating the spring stop proximallydecreases the compression on the spring, thereby allowing the device tobe adjusted to manipulate various loads.

Another embodiment of an energy absorbing device 430 is shown in FIGS.21A and 21B. In this embodiment, a non-circular link 432 is shown withan arbor base 434 having an arbor wall or casing 436, and a piston base438 having piston wall or casing 440. The non-circular cross-section ofthe link allows the walls or casings of the bases to have added materialmaking the walls thicker and therefore stronger. The added width of thewalls will reduce rotation during load adjustments. The walls or casingsof the energy absorbing devices 350, 350 a, 350 b, and 410 may be thinas previously shown or thicker as shown in FIGS. 21A and 21B.

Other forms of links can be used in the energy absorbing system 100 toabsorb any load placed on the system. As shown in FIGS. 22A and 22B, acircular link 450 is shown with an arbor base 452 including an arborshaft 454 with threads 456, and a piston base 458 including a piston 460that slides within the arbor shaft. There is also a spring stop 462 thatis threaded onto the threads of the arbor shaft, and the spring stop isin contact with a compression spring 464 that is in between the springstop and the piston base. There is a small finger lock 466 located onthe arbor shaft that locks the rotational position of the spring lock.To unlock the spring stop to adjust the load of the device, a tool, suchas a 2 mm rod, is inserted into the top of the link to depress thefinger lock, moving it away from a groove within the spring stop. Withthe spring stop unlocked, the rod is positioned through a radial divot468 of the spring stop. Adjustment occurs via multiple up and downactions or rocker of the rod. Depending on the pitch of the threads onthe arbor shaft, compression or decompression of the spring can rangefrom between about 1 mm to about 3 mm.

FIGS. 23A and 23B show another approach of a spring stop 470 thatincludes a first set of sloped notches 472 and a second set of slopednotches 474 that are sloped opposite to the first set. The spring stopis threaded onto threads 476 of arbor shaft 478. There is also a recess480 disposed through the threads of the shaft. A spring finger 482 (seeFIG. 23B) is built into the spring stop and engages the recess of theshaft. To further compress a spring 484, the spring stop is translatedin one direction using repeated rocking motions with a tool, such as a 2mm rod, that engages the first set of sloped notches. The spring stopwill longitudinally translate until the spring finger snaps into therecess of the shaft making an audible click. This audible click tellsthe user that the spring stop has been re-seated, which results inmoving the spring stop about 1 mm, or more depending on the pitch of thethreads on the shaft. To adjust the device by decreasing the compressionon the spring, the spring stop is translated in the opposite directionusing the tool to engage the second set of sloped notches in a repeatedmotion.

Yet another approach of a link 490 is shown in FIGS. 24A and 24B. Inthis embodiment a spring stop 492 is disposed on a shaft 494 of an arborbase 496. The inner surface of the spring stop includes raised bumps orteeth 498 that mesh with grooves 500 disposed on the arbor shaft. Thereis also a spring lock 502 on the spring stop that locks the spring stopin position on the shaft. To unlock the spring stop, a tool, such as a1-2 mm rod, is inserted into the spring lock. The unlocked spring stopis then free to slide distally about 1 mm then rotate about 30° to lockin place. This helical movement can compress the spring (not shown) inorder to adjust the device. The spring stop can also be unlocked andmoved proximally about 1 mm then rotated 30° in the reverse directionand locked in place to decrease the compression of the spring (notshown). The spring stop may slide distally or proximally more or lessthan 1 mm depending on the design of the grooves on the shaft.

Another embodiment of a link 510 is shown in FIGS. 25A and 25B. The linkincludes a spring stop 512 having a tooth 514 on its inner surface toengage grooves 516 and a recess 517 on an arbor shaft 518. The springstop also includes a spring finger 520 that prevents the spring stopfrom rotating or disengaging the grooves or recess of the shaft. Tounlock the spring stop, the spring stop is rotated about 60° via a tool,such as a 2 mm rod, that is inserted into an opened or closed end hole522 of the spring stop. The amount of rotation can be reduced byincreasing the number of radial teeth sets on the shaft. Once unlocked,the spring stop is slid along the shaft to a new location and thenrotated back 60° to lock the spring stop in position.

Referring now to FIG. 26, a link 530 is shown having a split-ring springstop 532 with a turnbuckle 534. Inserting a tool, such as a hex tool535, into the turnbuckle separates the split-ring to allow translationof the split ring to the next set of teeth 536 on a shaft 538, andcreates the shift via teeth on the hex receiving part 540. Thesplit-ring can be translated proximally or distally to adjust the loadmanipulating characteristics of the energy absorbing system.

FIG. 27 shows another embodiment of a link 550 having a spring stop 552with teeth 554 that is threaded onto threads 556 of a shaft 558. A tool560 with a preformed internal member and a hook 562 slides out of asheath (not shown) and wraps around the teeth of the spring stop.Pulling the tool creates rotation of the spring to translate the springstop along the threads of the shaft. This allows adjustment of theenergy absorbing device by increasing or decreasing the compression ofthe spring (not shown).

Another embodiment of a link 570 is shown in FIG. 28. In this embodimenta spring stop 572 is disposed over a shaft of an arbor base 574. Aspring 576 is positioned over the shaft and is located between thespring stop and a piston base 578. The piston base includes a piston orrod 580 that slides within the arbor shaft. To adjust the device,flexible helical shims 582 are inserted or removed from around the arborshaft proximate to the spring stop. An accessible housing 584 may beintegrated with the spring stop or positioned proximate to the springstop to capture the helical shims. A tool 586, such as a cannula orneedle with a rectangular cross-section, is used to insert shims intothe accessible housing. A tip of the tool is inserted into theaccessible housing and flexible helical shims are elastically deformedinto a generally straight line to be transported through the tool andinto the housing where the shims recoil or spring around the arborshaft. As shown in FIG. 28, the energy absorbing device is extended withzero load on the spring 576. There are six shims in position proximal tothe spring stop, giving adjustability from about 0 mm to about 6 mm.Shims may also be removed to adjust the profile of the load manipulationof the device.

An energy absorbing device 600 incorporating a push down mechanism forunlocking a load adjustment mechanism is depicted in FIGS. 29A-C. Inthis embodiment, the device is provided with a piston base assembly 604including a pivotable switch 606 including a bar extension 608. Thedevice 600 further includes a series of adjustable core plates 610, hereshown including four such plates. Each plate includes a pair of spacedholes 612 sized to receive a single arbor shaft 614 as with previouslydescribed approaches. It is noted that the arbor shafts extend from anarbor base including relief holes 617 in communication with bores forreceiving the piston shafts. Such relief holes 617 can be incorporatedas described into each of the disclosed embodiments to aid in avoidingbinding of the piston shafts. Moreover, the relief holes 617 can bevalved so that body fluid is drawn in during flexion of anatomy andthus, the structure acts as a pneumatic absorber for extension of theanatomy. The arbor shafts 614 include angled teeth 616 which engagecorresponding structure forming a perimeter of the spaced holes. Thiscorresponding structure can be in the form of ramps 618 which can belocked between the teeth 616 formed on the arbor shafts 614. Theinteraction between the core plates 610 and the arbor shafts 614 canprovide the tactile or audible feedback necessary to indicate relativemovement between the parts.

Each of the plates 610 also include a curved center slot 620, adjacentplates 610 having oppositely curved center slots 620. The slots 620 areconfigured to receive the bar arm 608 of the pivotable switch 606, whichextends generally perpendicularly through the plates 606.

Upon depression of the switch 606 an audible or tactile feedback canindicate the unlocking of the plates 610 from their engagement with thearbor shafts 614. That is, in a first position, the bar arm 608 of theswitch 606 can lock the plates 610 within the teeth 616 of the arborshafts 614. Once the switch 60 is depressed and caused to pivot, the bararm 608 moves within the center curved slots 620 of the plates 610,thereby allowing relative lateral movement of the plates to occur. Thelateral movement results in disengaging the plates from the arbor shafts614 to an extent allowing the translation of the plates along the arborshafts 614. By doing so, the operating length of the compression springs622 can be altered to thereby adjust the range of the load and energyabsorbing capabilities of the energy absorbing device 600. It is furthercontemplated that a tactile or audible click be induced as the plates610 are moved along the arbor shafts 614. The switch 606 can then bedepressed again to once again lock the plates 610 relative to the arborshafts 614.

In a related approach, as shown in FIGS. 30A-C, an energy absorbingdevice 630 includes a pivotable switch 632 which interacts with a bararm 634 extending from one of two adjustment core plates. A firstadjustment core plate 636 includes the bar arm 634 which extendstherefrom in a generally perpendicular manner. The second adjustmentplate 638 includes a channel 640 having an interior for receiving thebar arm 634. The switch 632 includes a terminal end portion 642 whichengages the bar arm 634 such that in a first position, the terminal endportion 642 forces the bar arm 634 against an internal wall of thechannel 640 to lock the plates 636, 638 in a longitudinal position alongarbor shafts 644. In this embodiment as well, the plates 636, 638include spaced through holes 646 sized and shaped to both receive thearbor shaft as well as lockingly engage teeth 648 formed on the arborshaft 644. Moreover, such engagement is contemplated to provide auditoryor tactile feedback necessary to indicate relative movement.

Upon depression of switch 632, the engagement between its terminal endportion 642 and the bar arm 634 of the plate 636 is relieved. Thisaction allows the plates 636, 638 to slide laterally with respect toeach other and out of a locking engagement with the arbor shaft 644. Atthis stage the plates 636, 638 can be moved longitudinally along thearbor shafts to thereby adjust the range of the load manipulationcapabilities of the compression springs 650. The switch can then bedepressed again, or alternatively simply released depending upon theparticular configuration of the switch, to lock both the plates 636, 638in position. This locking and unlocking action can again be associatedwith a feedback mechanism to alert the operator of status.

Turning now to FIGS. 31A-C, another embodiment of an energy absorbingdevice 652 including a switch is described. In this approach, the device652 includes a pivoting switch 654 operatively connected to a pin 656.Operation of the switch 654 results in longitudinal motion of the pin656 through center holes 658 formed in adjustment plates 660. Both theswitch 654 and the pin 656 ride within a center extension 662 which isconfigured between springs 664 configured about arbor shafts 666. Oneend of the center extension abuts a center most positioned adjustmentplate 668 of a stack of adjustment plates 670. Here also, the adjustmentplates 668, 670 include holes 672 for locking engaging teeth 674 of thearbor shafts 666 in a manner to provide feedback upon relative movement.The center holes 658 are again positioned and shaped to both cause theplates to lockingly engage the arbor shafts 666 as well as to movelaterally with respect to one another upon activation of the switch 654.When disengaged from a locking position, the adjustment plates 668, 670can be translated along the arbor shafts to adjust the springs 664.

Referring now to FIGS. 32A-D, yet another approach is described. Thus,it is further contemplated that an energy absorbing device 680 includestructure preventing accidental unlocking of adjustment structure. Aswith all of the disclosed embodiments, audible or tactile feedback isincorporated into the device 680 to alert the patient or operator as tostatus concerning a locked or unlocked state as well as relativemovement of parts during adjustment. Adjustment core plates 682, 684each include curved wings 686 which extend longitudinally along thedevice 680 exterior of springs 688 configured about arbor shafts 690.Moreover, the plates 682, 685 each include spaced holes 692 withperimeter for lockingly engaging teeth 694 formed on the arbor shafts690 and for providing necessary feedback concerning positioning ormovement.

The energy absorbing device 680 also includes a piston base 696including a center extension 697 configured between the springs 688. Atan opposite side of the device 680 and adjacent the arbor base 697 thereis positioned a center extension 698.

Pivotably attached to the center extension 698 is a switch 700 assembly.As best seen in FIG. 32D, the switch assembly includes a first extension702 including a slot sized to receive a U-spring 703 and a secondopposite end portion equipped with a tail 704. The tail 704 is sized andshaped to lockingly engage corresponding structure (not shown) formed inthe piston base extension 697. The U-spring 703 includes ends 705 whichextend through holes both round 706 and slotted 708, formed in theplates 682, 685.

In use, the switch assembly 700 operates to retain the U-spring 703 inan orthogonal position through its engagement with the adjustment plates682, 684. The U-spring 703 in turn locks the adjustment plates 686, 684against the arbor shafts 690 and within its teeth 694. Upon depressionof the switch 700, the extension 702 disengages from the U-spring 703thereby permitting the U-spring to be bent and thus, unlocking thedevice. Next, the curved wings 686 of the adjustment plates 682, 684 canbe depressed to disengage the plates from the teeth 694 of the arborshafts 690 so that translation of adjustment components is possible. Aspreviously described, such translation results in altering when thecompression springs will manipulate loads. The wings 686 are thenreleased to set the longitudinal position of the plates on the arborshaft. After desired adjustment is accomplished, the switch can bere-seated to thereby again lock the plates 682, 684 in position.

An approach to an energy absorbing device 710 including a spring loadedspacer assembly 712 is shown in FIGS. 33A-C. In this approach, ratherthen relying on a locking engagement with arbor shafts 714, anadjustable spacer 716 of the spacer assembly 712 can be translated andlocked in place spaced from the arbor base 716. This approach avoids theremoval of material from arbor or link shafts, thus preserving thestructural integrity of such members. To accomplish this the spacer 718with pin 720 extending laterally therethrough is moved towards thepiston base as best seen in FIG. 33B. So advancing the spacer 718results in the pin engaging a slot formed in a spring biased nut 722configured within the spacer 718. It is to be noted that the springbiased nut 722 is placed in apposition with the compression springs 724.Once the pin 720 is locked within the nut 722, the spacer 718 benefitsfrom the positional relationship between the nut 722 and the springs 724such that a desired adjustment in energy absorbing capabilities of thespring is achieved. Moreover, it is to be recognized that a compressibledome (not shown) can be configured over the pin to provide a desirableouter profile.

In an approach which relates to the immediately preceding device, ratherthan a pin, the energy absorbing device 730 can include a lever 732which is accessible through a compressible dome 734. In this regard, thelever 732 can be held in an inactive state by pins or suture (not shown)after implantation during a time when natural bone and tissue can growover the energy absorbing device 730 to aid in its fixation at aninterventional site. Such pins or sutures can subsequently be removed toactivate the device so that desired energy absorbing is accomplished.Structure holding an energy absorbing device in an inactive state can beincorporated into any one of the devices disclosed herein. In thepresent embodiment, when in an inactive state, the device 730 can bemade to move through a normal range of motion with the only force beingapplied by the device 730 would be that generated by springs 735 of anadjustable spacer assembly 736.

Once the lever 732 is permitted to operate without constraint (such asby removing the sutures or pins), an operator can cause the lever 732 topivot by applying a force through the dome 734. In its rotated position,the lever 732 which is pivotably supported by a spacer 738, causes thenut 740 housed within the spacer 738 to translate longitudinally awayfrom the arbor base 742. The spacers 736 translate longitudinally withthe translation of the nut to thereby bring the compression springs 724into the load manipulating capabilities of the device 730.

FIGS. 35A-E depict an approach where adjustment structures can beadditionally attached to cooperate with piston shafts of an energyabsorbing device 750. In this approach, pins 752 (See FIG. 35C) attachedto adjustment plates 754, 756 including curved side wings 758 aretranslatable within slots 760 formed through arbor shafts 762. Thepiston shafts 764 additionally include cut-outs 766 along which the pins766 are translatable. Accordingly, in addition to adjusting the positionof the blocks 754, 756 along the arbor shafts to adjust the absorberfunctioning of the compression springs 768, through the engagement ofthe pins 766 with the piston shafts 764, further adjustment can beachieved.

Moreover, whereas the adjustment assembly can include all of thestructures necessary to cooperate with the anchor shaft 762, acontemplated alternative approach is to break the assembly into furthersub-components. In this regard reference is made to FIGS. 36D and Ewhich depict five components defining an adjustment assembly which couldreplace a two-piece approach. Thus, in addition to adjustment plates770, 772 including curved wings 774, a series of three additional plates776 can form the adjustment assembly. In this way, the detailedmachining or forming which would be necessary to be configured into twopieces can be spread through further components thus streamliningmanufacturing procedures.

Turning now to FIGS. 36A and B, an adjustable, interlocking link device780 for an energy absorbing device is shown. The link device 780includes a pair of longitudinally configured shafts 782, 784 havingthreads 786. The shafts each include ball ends 788 for attaching to amount of a complete energy absorbing system such as that depicted inFIG. 1A. Configured about the thread shafts 782, 784 are a pair ofsliders 790, each of the sliders defining curved arms extendinglongitudinally. The threaded shafts 782, 784 can be rotated to extendthe overall length of the assembly. In this way, rather than relying onan adjustable spacer or other structure to alter the load manipulatingability of an energy absorbing device, adjusting the length of theinterlocking link 780 can be employed to accomplish the same. In thisregard, the energy absorbing assembly can be configured with one or moretie-rods the ends of which can be accessed to adjust both length of theassembly and effective spring height. For example, one end of a tie-rodcan be rotated to adjust length and another end or a second tie-rod canbe rotated to alter an amount of pre-loading of a spring.

One form of a link assembly 790 can incorporate structure permittingintra-operative or post-operative activation or adjustment (See FIG.37). While shown for use in the particular link assembly 790 depicted,such or similar structure can be used in each of the approachesdisclosed herein. As shown in FIG. 37, a spring 792 can be configured toeffectively control positioning and loading of link ends 794, 796. Arelease wire 798 can be placed into engagement with the spring 792 toretain it in a compressed configuration so as to cause it to beinactivated. Intra-operatively, the release wire 798 can be manipulatedto permit the spring 792 to accomplish load manipulation. Alternatively,the release wire 798 can be manipulated by nicking the skinpost-operatively to activate the spring 792.

It has also been contemplated that an implantable sensor unit can beconfigured at an interventional site to detect and keep track ofindicators associated with changes in tissue density. One approach isdescribed in WO 2007/098385, the entire contents of which areincorporated by reference. The implantable sensor unit can be configuredfor wireless communication with an external device and the externaldevice can also be configured for wireless communication with theimplantable sensor unit. In particular, the external device is adaptedfor retrieving, storing, and displaying, in human intelligible form, thetissue density data detected by the implantable sensor unit. Theimplantable sensor can additionally be affixed to bone of the skeletalsystem such that it may monitor the bone, adjacent soft tissues, such asmuscles, nerves and connective tissues. The sensor may be within orintegral to an artificial implant attached to the skeletal system,attached to an artificial implant, adjacent to an artificial implant, orany combination of these locations.

The implantable sensor can include a sensor, a signal processor, amemory unit, a telemetry circuit, and a power source. The sensor can bean acoustic transducer responsive to acoustic signals transmittedthrough human tissue. Further, it is fully contemplated that the sensormay include other electronics and components adapted for monitoringindicators of changes in tissue structure including deterioration and/orhealing. The disclosed sensor has applications throughout the skeletalsystem including the hip, knee, ankle, elbow and jaw joints and loadbearing bones such as the skull and long bones. Such disclosed sensorsare useful to evaluate tissue properties and detect changes to tissue inthe skeletal system. The sensor also has a particular application withrespect to detecting changes in bone density as it relates toosteoporosis and the sensor can detect tissue density changes withrespect to tissue around fixation implants, joint implants, or any othertype of implant. Moreover, an acoustic sensor may also be used to detectchanges in viscosity. Thus, the sensor may be utilized to listen forchanges in bodily systems and organs and alert healthcare professionalsto any impending or potential problems.

Accordingly, a number of embodiments are described above for adjustingthe amount of load an energy absorbing device can manipulate to helpreduce pain in a patient. These embodiments can be used in any energyabsorbing system for use throughout the body but have clear applicationsto articulating body structures such as joints. Moreover, features andstructures of certain of the disclosed embodiments can be incorporatedinto other disclosed embodiments by replacing structure or complementingstructure.

It will be apparent from the foregoing that, while particular forms ofthe embodiments have been illustrated and described, variousmodifications can be made without parting from the spirit and scope ofthe invention.

1. An implantable system for manipulating energy transferred by membersdefining a joint, comprising: a first attachment structure configured tobe attached to a first member of the joint; a second attachmentstructure configured to be attached to a second member of the joint; andan adjustable energy manipulation device attached to the firstattachment structure and second attachment structure, the adjustableenergy manipulation device includes one or more adjustable mountassemblies.
 2. The system of claim 1, wherein the adjustable mountassembly includes a ball and socket arrangement.
 3. The system of claim2, wherein the ball includes an extension including teeth.
 4. The systemof claim 3, wherein the adjustable mount assembly further includes amount having an interior sized to engagingly receive the extension ofthe ball.
 5. The system of claim 4, wherein the mount assembly includesa spring lock which locks relative movement between the extension of theball and the mount.
 6. The system of claim 1, wherein the adjustablemount assembly alters a length of the adjustable energy manipulationassembly to thereby change its loading characteristics.